In ophthalmic surgery, and in particular in vitreo-retinal surgery, it is desirable to use a wide-angle surgical microscope system to view as large a portion of the retina as possible. Wide-angle objective lenses for such microscopic systems exist, but they require a wider illumination field than that provided by the cone of illumination of a typical fiber-optic probe. As a result, various technologies have been developed to increase the beam spreading of the relatively incoherent light provided by a fiber-optic illuminator. These known wide-angle illuminators can thus illuminate a larger portion of the retina as required by current wide-angle surgical microscope systems.
It is also known to incorporate optical fibers into the working end of a surgical instrument. This eliminates the need for a separate illumination port and offers the advantage of directing the light beam together with the instrument onto the target site. Instrument sizes must, however, be correspondingly increased and larger sclerotomies may be necessary. An alternative procedure is to employ an illuminated infusion cannula to integrate the infusion and illumination functions at a single point.
One example of a combined infusion cannula and illumination source is given in U.S. Pat. No. 4,820,264. The '264 device comprises an infusion channel through which light transmitting fibers are passed for directing light into the eyeball at the point of discharge of the intraocular irrigating solution. Such illumination is not automatically directed by manipulation of the cutting instruments. Moreover, the fibers are run directly within the infusion channel, and illumination and infusion portions are non-separable near the eye.
These prior art combined infusion cannulas, however, exhibit various disadvantages. These disadvantages include undesirably low light transmittance and undesirable fluid flow rates, particularly when combined in, for example, a 20 gauge cannula.
Therefore, a need exists for an illuminated infusion cannula that can reduce or eliminate the problems prior art combined cannulas, particularly low light transmittance and low fluid flow rates.